Type checking and conversion in R Programming - Cheat Sheet & Quick Revision

Recall & Review

beginner

What function in R checks the type of an object?

The typeof() function returns the internal type or storage mode of any R object.

beginner

How do you convert a numeric value to a character string in R?

Use the as.character() function to convert numeric values to character strings.

beginner

What does the is.numeric() function do in R?

It checks if an object is of numeric type and returns TRUE if it is, otherwise FALSE.

intermediate

How can you convert a character vector to a factor in R?

Use the as.factor() function to convert a character vector into a factor, which is useful for categorical data.

intermediate

What happens if you try to convert a non-numeric character string to numeric using as.numeric()?

R returns NA with a warning because the string cannot be interpreted as a number.

Which function checks if an object is a character vector in R?

A is.character()

B as.character()

C typeof()

D is.numeric()

The is.character() function returns TRUE if the object is a character vector.

What does typeof(42L) return in R?

A "integer"

B "double"

C "numeric"

D "character"

The suffix L makes 42 an integer, so typeof(42L) returns "integer".

Which function converts a factor back to a character vector?

A is.factor()

B as.factor()

C as.character()

D typeof()

Use as.character() to convert factors to character vectors.

What will as.numeric("abc") return?

A An error stopping the program

B 0

C "abc"

D NA with a warning

R returns NA and a warning because "abc" cannot be converted to a number.

Which function tells you the class of an object in R?

A typeof()

B class()

C is.numeric()

D as.character()

class() returns the object's class, which is a higher-level description than typeof().

Explain how to check the type of a variable and convert it to another type in R.

Think about functions that check type and those that change type.

Describe what happens when you try to convert a non-numeric string to numeric in R and how to handle it.

Consider what R returns and how you might check for conversion success.